A typical print head design passes ink from an ink reservoir at the back of the print head to the jet stack at the front of the print head through various layers of metal, polymer and and/or adhesive layers. The ink passes through a fluidic channel that penetrates these layers one of which is a flex circuit. The term flex circuit as used here means a polymer layer, such as polyimide, having electrically conductive traces that route near and around the clearance holes that pass through the print head. These traces have a topography associated with them that makes sealing around the ink ports difficult, even when using compliant adhesives.
Because of the topography, when the layers are pressed together leaks sometimes occur within layers. If the ink leaks into any layer upon which electrical signals run, they will short out and the print head will not operate. In addition, leaks alter the pressures of the ink flows in the print head which can cause other problems.